Air Management and Pressurization Series

As we bring our first series about air management in a hydronic system to a close, we’re going to revisit tanks – not what they do (we’ve already covered that) but what we call them. Specifically, we want to address whether or not there is a difference between what some industry professionals call an “expansion tank” and what others call a “compression tank.”

Properly sized expansion tanks (standard or bladder/diaphragm) are critical to a successful air management in a hydronic system.

Every expansion tank manufacturer has a written form that provides the steps and calculations for sizing an expansion tank. Most, if not all, have developed software that does the work for you. Bell & Gossett has a great one, ESP-Plus which can be downloaded here. But regardless of whether you use software or charts and longhand calculations to size an expansion tank, there are a few pieces of information you’re going to have to have either way. These key values are:

Air must be managed in every type of closed hydronic system, either by (1) routing it to a specific place in the system where it can’t create problems like pipe corrosion or air blocking of components, or (2) by continuously eliminating it

Closed loop systems create the need for accurate pressurization and air management in a hydronic heating and cooling system. Unfortunately, proper air management often turns out to be an Achilles’ heel in a hydronic system’s design. Design it wrong and a host of problems can erupt, from noisy operation to poor efficiency and shortened equipment life. It begs the question -- why even design a system to be closed in the first place? After all, condensate systems and cooling tower systems are